When playing those naming games and pub quizzes, nobody ever mentions Sweyn Forkbeard. Okay, so he was England's shortest-reigning king but he was declared King of England, on Christmas day 1013.
For twenty years the Danish Viking waged war on England, first with Olaf Tryggvason and later with his son, Canute. He had a troubled life and deposed his father Harold Bluetooth in Denmark before turning his attentions to England. In the decisive, brutal invasion, where women were burned alive, children impaled on lances and men died suspended from their private parts.
So how come we know so little about him?
Gainsborough historian Darron Childs says: "It is perhaps one of the reasons why Sweyn has been largely forgotten. It's hard to make a big thing of someone so bad - it would be a bit like celebrating Hitler. It's a difficult thing to try and overcome."
However, he adds: "He was part of a dynasty that changed the course of this country. And he wasn't any different to many of his contemporaries. People like Ethelred, who were equally as bad - if not worse."
Ethelred the Unready, king of England (978-1013 and 1014-1016) had ordered the slaughter of all Danes living in England in 1002, in what became known as the St Brice's Day Massacre.
Another reason why Sweyn's story remains largely untold may be the lack of physical evidence. And the chroniclers of the time painted him as an evil baddie, a typical Viking, possessing all of the pagan savagery. Sweyn's reputation was villainous. Unlike his son, Canute, who was a Christian and historians look more favourably on him.
However, he was pivotal to the development of English history. His legacy was in Canute who became known in some quarters as 'the great' when he became king of England, Denmark and Norway. Viking DNA is now part of our royal bloodline as well as the rest of us English folk.
Sweyn reigned for just forty days. He died on 3 February 1014 in Gainsborough, Lincolnshire. He was killed but there are no records of a body nor a grave. So what happened to him?
One popular theory is he was murdered by the ghost of St Edmund, who was himself killed by Sweyn's Viking predecessors. It is said that he returned from the grave in the dead of night during Candlemass and took his revenge with a spear.
Who knows? Just remember that he was England's shortest-reigning king, in case it comes up in the pub quiz.